During the Second World War, Biggles goes missing whilst trying to rescue an Italian princess from occupied France. Given up for dead by Colonel Raymond, his colleagues don't give up so soon and instead infiltrate the region to try and determine his whereabouts.

Ginger, Bertie and Algy parachute into occupied France and immediately split up to try and track down Biggles. Ginger, disguised as a Spanish onion seller, ends up getting shot and falling in love before meeting up with Biggles in a deserted village full of cats. Bertie, disguised as a travelling musician (?) meets up with his old boatman and boat, and gets thrown off a cliff. Algy gets the easier option - avoiding capture by knocking out a policeman and then pedalling several miles to find the others.

It turns out Biggles is alive, and being cared for by the Princess. After a sidetrip to rescue Henri, their earlier pilot, the team hatch a plan to hijack an Italian flying boat and escape. The plan goes almost without a hitch, and they end up crash-landed on a beach in Algeria.